Chemistry Questions (rating:easy)

[psychlaw]

Lots of q's posted here eventually

For Now

(1) Balance this equation, I don't know how to do subscript numbers so I'll try and write/explain it as best as I can
NaOH + Cl2 --> NaCl + NaClO3 + H20 (this is water, not H and two oxygens)



Also

(2) Iron Pyrites has the forumula FeS2 (2 is a subscript ). When this solid is roasted in air, it reacts to form iron (III) oxide and sulphur dioxide gas.
What mass of iron (III) oxide is obtained by the roasting of 5000kg of iron pyrites which is 60% pure?


Thanks all

[Toothpaste]

[psychlaw]

thanks

[Collin Li]

Each mole of makes 0.5 moles of , agree?

This is because the elements balance (same number of Fe).

So, if I have 5000kg of iron pyrites of 60% purity, then I really only have:

kg of .

Now, convert to moles, then multiply by half (because that's how much iron (III) oxide you'll make), and then multiply by the molar mass to get back to mass)

kg

Note that the fraction on the right is the molar mass of iron (III) oxide divided by the molar mass of iron pyrite. This effectively converts the mass of iron pyrites into the mass of iron (III) oxide (divide by molar mass of iron pyrite to get moles, then multiply by molar mass of iron (III) oxide to get mass).

[Collin Li]

NaOH + Cl2 --> NaCl + NaClO3 + H20 (this is water, not H and two oxygens)

One thing I always find weird is that I see "H20" commonly written, as opposed to "H2O". Why do people think the oxygen is a "0" (zero)?

Anyway, I made this post to point out that anyone who can read chemical notation should understand that the 2 belongs to the H.

The only time when the preceding number tells you about following item is when there is a big number before an entire species in a reaction. For example: H2SO4 + 2NaOH --> NaSO4 + 2H2O

In H2O, the 2 is in the middle of a species, so it definitely means the 2 is going to be a subscript, and hence, the 2 belongs to the element it is a subscript to (Hydrogen).

I don't know if you already knew this, but I'm just pointing it out.

[lanvins]

There aren't any answers in the back of the book(my answers are in red). I'm a little unsure about the solute part, do you use mole ratios? Can you assume it's at 25oC? Thanks

[orangez]

Not all of it is correct -- I'd suggest you writing out balanced equations and working out the mole ratios, and then applying [H3O+].[OH-] = 10^-14 to find [H3O+] and [OH-].

[Mao]

solution	solute(M)	H3O+	OH-
HCl	0.01	0.01	10-12	acidic
HNO3	0.03	0.03	3.33*10-13	acidic
NaOH	0.02	5*10-13	0.02	basic
Ca(OH)2	0.001	5*10-12	0.002	basic

[psychlaw]

I think I've got this question right, but I don't have the answer so can someone do it so I can compare my answer to it.

In the blast furnace, iron (III) oxide reacts with carbon monoxide to form iron and carbon dioxide. Carbon monoxide is a gas which forms in the blast furnace as a result of reaction between carbon and oxygen at a high temperature.

(1) What mass of iron may be obtained from 2250 kg of iron (III) oxide?

(2) What mass of carbon must be present to produce 1000 tonne of iron?

[Collin Li]

converts into 2 , so:

kg of iron

To produce 1000 tonne of iron by carbon, first we need to balance the equation to find out the stoichiometric ratio:

Balanced equation:

And, carbon monoxide is formed by:

Now, let's do this in a methodical way (the above solutions I've offered have been an 'express' method because they were pretty simple questions):

[psychlaw]

thanks man

Also with your last post, answering my question about the iron pyrites, what is the "159/120" for?
Isn't it supposed to be 3000/120 for the mol calculation. The 3000 is the mass and the 120 the molar mass?

[Collin Li]

Yeah, I did it all in one step. I divided by 120, then multiplied by 159 (the molar mass of iron (III) oxide).

Normally, you'd divide by 120 first, write down the number of moles, then multiply by 1/2, write down the number of moles of that, then multiply by the molar mass, to get the mass, which takes 3 lines! I took 1.

[psychlaw]

When Calcium Carbide, CaC2, is added to water, a vigorous reaction occurs producing ethyne gas, c2h2 and calcium hydroxide. What mass of ethyne os produced when 80g of calcium carbide is added to 50g of water?


This is the easiest of 10 questions I have to do (but at the moment I have no clue how to do them) so if somebody could please just do this question for me, so then I can work out the rest using this as the example:D
thanks guys!!!

[Mao]

(calcium oxide is slightly soluble)





since the number of moles of water is more than double that of calcium carbide, calcium carbide is our limiting reactant:

stoichiometry: the mole ratio of ethyne to calcium carbide (from the equation) is 1:1, hence

[psychlaw]

what exactly do u mean by

n (c2h2) = n(CaC2) = 1.248 mol?

I think im lost because there arent any numbers or answers =/